Flask



FIG. 1 is a front perspective view of the flask, showing my new design;

FIG. 2 is a front facing view thereof, the rear left and right side views being identical thereto, except for the position of the nozzle outlet;

FIG. 3 is a bottom plan view thereof; and,

FIG. 4 a top plan view thereof.

The broken lines are included for the purpose of illustrating visible, interior features that form no part of the claimed design. 

The ornamental design for a flask, as shown and described. 